Biotic Control of Earth's Climate: An Ecohydrological Perspective on the Phanerozoic Temperature Record

TL;DR

This paper presents a unified ecohydrological framework explaining Earth's long-term climate stability over the Phanerozoic by linking biological, geochemical, and hydrological processes that create climate thresholds.

Contribution

It introduces a novel integrated model combining weathering, vegetation, and climate feedbacks to explain Earth's temperature regulation over hundreds of millions of years.

Findings

Identification of two climate thresholds at 15°C and 33°C.

Recurrent shifts in climate states linked to biological innovations.

Biosphere acts as an active regulator of Earth's climate.

Abstract

We propose a unified framework linking silicate weathering feedbacks, ecohydrological optimality and vegetation-climate interactions to explain Earth's Global Average Temperature evolution over the Phanerozoic. The framework integrates two complementary processes: (i) solute-transport-limited weathering, which governs long-term carbon sequestration, and (ii) ecohydrological optimality, which constrains vegetation productivity through the balance between water availability and carbon uptake. Together, these processes establish two emergent climatic thresholds, around 15 {\deg}C and 33 {\deg}C, that define a stable corridor for the Earth system. Below 15 {\deg}C, declining evapotranspiration and rising albedo accelerate cooling; above 33 {\deg}C, heat and water stress suppress vegetation and limit further warming. Analysis of ten independent studies (2019-2024) confirms the recurrent appearance of these thresholds in both modern ecosystems and Phanerozoic temperature reconstructions. Major biological innovations, such as the colonization of land by plants, the rise of forests, and the emergence of $C_4$ photosynthesis, have reorganized these feedbacks, repeatedly shifting the planet between quasi-stable climate states. The resulting picture is one in which the biosphere acts as an active regulator of climate, modulating and at times overriding geochemical feedbacks. This framework unifies climate, tectonics, and life into a single ecohydrological system, offering a coherent explanation for the bounded variability of Earth's temperature across 500 million years and insight into its future resilience. This perspective challenges the view of life as a passive climate responder, positioning the biosphere as an active regulator. Understanding these self-stabilizing mechanisms offers critical insight into how Earth might respond, or fail to respond, to ongoing human-driven climate perturbations.